In 1932, James Waters Bendell picks up a magnificently sculpted hitchhiker named Ares Sen Kenlin (the Sen means he’s a scientist, but Waters is just a name) who says that he’s trying to get back to his home time (3059) from seven million years in the future—a time when mankind has atrophied because of their reliance on machines.

Bob Carter takes a plane up to 45,000 feet to test an anti-gravity device, but instead it hurls him into the same future as the story “Twilight”—but whereas the earlier story had mankind who were dying out in 7,000,000 A.D. because of the ubiquity of machines, Carter finds himself billions of years beyond that, with both man and (most) machines long gone.

Millions of years after mankind raised various species and sent them to the stars, one of the species returns and believes that humans have fallen into a primitive existence. And the time travel? Partway through the story, there’s a power source that goes to the end of time and cycles back to the beginning of time. In addition, Fred Galvin pointed out to me that even though it takes the aliens six years to travel to Earth, when they return to their home planet, only one year has passed, apparently a complete undoing by Seun of Rhth of the alien invasion.

The story also appeared in Healy and McComas’s seminal anthology, Adventures in Time and Space, and it was made into a one-act play in 1943 by Wayne Gordon.

From Dec 1957 to Jun 1958, John W. Campbell himself hosted this radio series for the Mutual Broadcasting System. Many episodes were written by John Flemming, and although there was no official connection between the show and Campbell’s Astounding, many other scripts were by Campbell’s stable of writers including Poul Anderson, Isaac Asimov, Philip K. Dick, Gordon R. Dickson, Murry Leinster, Robert Silverberg and George O. Smith (“Time Traveler”). There were at least three time-travel episodes.